Artificial hair fiber, use thereof and process for producing the same

ABSTRACT

The present invention provides an artificial hair fiber having a good balance between a feel and a curly characteristic. The present invention also provides an artificial hair fiber having a better hackling efficiency and weaving efficiency, a fiber bundle for artificial hair, and a process for producing the same. Artificial hair fibers possess desired properties, the fibers having a flexural rigidity of from 0.001 to 0.01 gf·cm 2  or being subjected to crimping in which a crimp wave shape satisfies the following formulae: 0.2 mm≦R≦3 mm, 1 mm≦L≦15 mm, (wherein R is a length from the top to the bottom of a crimp wave shape), and (wherein L is a length between the tops (or between the bottoms) of a crimp wave shape).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase of PCT International Patent Application No PCT/JP2010/055266, filed Mar. 25, 2010, and Japanese Patent Application No 2009-100448 filed Apr. 17, 2009, in the Japanese Patent Office, the disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to artificial hair fibers used for a hair decoration

2. Description of the Related Art

As an artificial hair fiber, a variety of fibers are commercially available, including a polyvinyl chloride fiber, a polyamide fiber, a polyester fiber, and the like. The fibers are properly used depending on their style or use.

Research has been conducted that allows an artificial hair fiber to approach a texture of natural hair or that imparts superior performance than that of the natural hair to the artificial hair fiber. Examples of evaluation items for the artificial hair fiber include a flexural rigidity, curl uniformity, a hackling efficiency, a weaving efficiency, a feel, and the like. For example, Patent Document 1 and Patent Document 2 describe an artificial hair fiber having a flexural rigidity close to that of natural hair. Patent Document 3 describes that artificial hair fibers are made to be crimped so as to add a shape and a texture close to natural hair to the fibers.

Generally speaking, in order to maintain curl uniformity in the artificial hair fiber, rigidity under a fiber bundle state is necessary. However, stronger rigidity causes a poor soft-feel. Weaker rigidity results in a poor uniform curly characteristic while having an excellent feel. Affected by properties other than the rigidity in some cases, the curl uniformity is difficult to be controlled. In Patent Document 4, a fiber bundle for artificial hair having both improved curl uniformity and feel has been obtained by mixing two types of original yarn having a specific rigidity and sectional shape.

Hackling (combing) may be carried out for artificial hair fibers used for a hair decoration such as wigs, weaves, hair pieces, braids, extension hairs, and accessory hairs. This hackling can be performed by placing a fiber bundle for artificial hair over a large metal brush on which metal rods having a length of several dozen centimeters are made to stand vertically with a distance of several centimeters therebetween, and by pulling an end of the bundle off the metal brush. Unfortunately, during this hackling work, the fibers may get caught in the metal brush and some of the fibers cannot be employed as a product (Patent Documents 5 to 7). In addition, smoothing of the surface of the fibers can decrease their resistance, thereby reducing a chance of getting caught during hackling. However, their easy-to-weave characteristic becomes poor.

In order to improve a hackling efficiency, an easy-to-weave characteristic, and a feel, Patent Document 8 describes that crimping has been carried out for artificial hair fibers having a cross-sectional shape that two “+” are joined side by side (hereinafter, sometimes referred to as a “double-cross shape”) or having a cross-sectional shape that three “+” are joined (hereinafter, sometimes referred to as a “triple-cross shape”).

In order to improve the hackling efficiency, Patent Document 9 describes that crimping has been carried out for artificial hair fibers.

PRIOR ART REFERENCE Patent Document

-   [Patent Document 1] JP-2008-69505A -   [Patent Document 2] JP-2007-291541A -   [Patent Document 3] WO-2005/099502 -   [Patent Document 4] WO-2006/135059 -   [Patent Document 5] JP-2002-227018A -   [Patent Document 6] JP-2002-315765A -   [Patent Document 7] JP-2002-249914A -   [Patent Document 8] JP-H11-309275A -   [Patent Document 9] WO-2008/035712

SUMMARY OF THE INVENTION

Unfortunately, the conventional arts as described in the above documents have had room for improvement with regard to the following points.

Artificial hair fibers disclosed in Patent Documents 1 and 2 remain undefined in terms of curl uniformity, a hackling efficiency, and a weaving efficiency. These fibers have a double structure including a sheath portion and a core portion, which leads to poor uniformity and requires complicated production steps. Artificial hair fibers disclosed in Patent Document 3 remain undefined in terms of rigidity, curl uniformity, a hackling efficiency, and a weaving efficiency.

Artificial hair fibers disclosed in Patent Documents 5 and 6 remain undefined in terms of rigidity, curl uniformity, a hackling efficiency, a weaving efficiency, and a feel. Artificial hair fibers disclosed in Patent Document 7 remain undefined in terms of rigidity, curl uniformity, and a weaving efficiency. Artificial hair fibers disclosed in Patent Document 9 remain undefined in terms of rigidity, curl uniformity, a weaving efficiency, and a feel

In Patent Documents 1 to 3, 5 to 7, and 9, artificial hair fibers having both better curl uniformity and feel have not been obtained. In Patent Documents 1 to 3, 5 to 7, and 9, artificial hair fibers having both better hackling efficiency and weaving efficiency have not been obtained.

Patent Document 4 describes a method for improving both curl uniformity and feel. However, this method requires adjustment of a fiber bundle for artificial hair by mixing two types of original yarn having a specific rigidity and sectional shape as described in Patent Document 4. Thus, in the case of using one type of original yarn or in the case of using two types of original yarn which does not satisfy the specific condition, the curl uniformity and feel have not been able to be improved.

Patent Document 8 describes a method for improving both a hackling efficiency and an easy-to-weave characteristic. However, fibers having both the improved hackling efficiency and easy-to-weave characteristic include only fibers having a double-cross shape or a triple-cross shape in their cross-sectional shape. Therefore, in the cases of artificial hair fibers having other cross-sectional shapes, the hackling efficiency and the easy-to-weave characteristic have not been able to be improved.

It is an object of the present invention to provide an artificial hair fiber having a good balance between a feel and a curly characteristic, use thereof, and a process for producing the artificial hair fiber

The present invention provides an artificial hair fiber having a flexural rigidity of from 0.001 to 0.01 gf·cm² as measured by the KES method, wherein the fiber is formed of a synthetic resin.

Examples of a sectional shape of this artificial hair fiber in the widthwise direction may include an elliptical shape, a circular shape, a glasses shape, a cocoon shape, a 6-leaf flower shape, and an 8-leaf flower shape. The sectional shape may be a single or mixed shape thereof.

The synthetic resin which forms the above artificial hair fiber may be a polyvinyl chloride resin.

The above artificial hair fiber may be a polyvinyl chloride fiber produced by melt-spinning a polyvinyl chloride resin.

The above polyvinyl chloride resin may contain 100 parts by mass of a vinyl chloride resin and 0.5 to 10 parts by mass of a chlorinated vinyl chloride resin.

The synthetic resin which forms the above artificial hair fiber may be at least one synthetic resin selected from the group consisting of nylon 6, nylon 6/6, nylon 4/6, nylon 1/2, nylon 6/10, and nylon 6/12.

The synthetic resin which forms the above artificial hair fiber may be a modacrylic resin.

A wave shape of the above artificial hair fiber may fit within a range of the following formulae:

0.2 mm≦R≦3 mm, 1 mm≦L≦15 mm,

(R: amplitude of a wave of the fiber in the widthwise direction), and

(L: a cycle length of a wave of the fiber in the lengthwise direction).

The above artificial hair fiber may be an artificial hair fiber whose wave shape is formed by gear-crimping.

The present invention provides a fiber bundle for artificial hair produced by bundling the above artificial hair fibers.

The present invention provides a curly hair decoration using the above artificial hair fibers.

The present invention provides a woven hair decoration using the above artificial hair fibers.

The present invention provides a braid using the above artificial hair fibers.

The present invention provides an extension hair using the above artificial hair fibers.

The present invention provides a process for producing an artificial hair fiber, comprising:

-   -   a mixing step of mixing a vinyl chloride resin and an additive;     -   a melt-spinning step of melt-spinning a co position containing         the mixed vinyl chloride resin at a spinneret temperature of 160         to 190° C.;     -   a stretching step of stretching melt-spun fibers under an         atmosphere at a stretching temperature of 90 to 120° C., at a         stretching ratio of 200 to 400%;     -   a thermal relaxing step of subjecting the stretched fibers to         thermal relaxing treatment under an atmosphere of air at a         temperature of 110 to 140° C. until the entire length of the         fibers becomes 60 to 95% of the length following the stretching         step; and     -   a crimping step of crimping the fibers after the thermal         relaxing treatment step.

The crimping of the above production process may be gear-crimping carried out at a depth of gear waves of 0.2 mm to 6 mm, a gear surface temperature of 30 to 100° C., and a processing rate of 0.5 to 10 m/min.

Examples of an orifice shape of the spinneret which is used in the melt-spinning step of the above production process include a circular shape, a cocoon shape, a Y-shape, an H-shape, and an X-shape. The spinneret may have a single or mixed shape thereof.

The present invention has been able to produce an artificial hair fiber having a good balance between a feel and a curly characteristic. In addition, the present invention has been able to produce a fiber bundle for artificial hair having an excellent weaving efficiency and feel almost without getting caught during hackling.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic diagram showing a crimp wave shape of a fiber bundle for artificial hair of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention are illustrated in detail. In order to avoid redundancy, explanation for similar contents is not repeated.

Embodiment 1 Artificial Hair Fiber

Qualities of an artificial hair fiber according to the present invention tend to be enhanced when the flexural rigidity measured by the KES method of the artificial hair fiber is moderately large because the artificial hair fiber with such a large flexural rigidity can maintain a gear wave shape and the crimps thereof is not easily undone. In contrast, when the rigidity is moderately small, the feel of the artificial hair fiber tends to be enhanced. Because of the above, the flexural rigidity, as measured by the KES method, of the artificial hair fiber according to this embodiment is preferably between 0.001 and 0.01 gf·cm², and more preferably between 0.002 and 0.008 g·cm².

It has been demonstrated in Examples below that the above artificial hair fiber is excellent in curl uniformity and feel. Because of this the above artificial hair fibers are particularly suitable for an application which is utilized to make the artificial hair fibers curled or for a curly hair decoration. The curly hair decoration as used herein includes a hair decoration to which a curly shape has been imparted at sales or distribution stage or a hair decoration which is on sales or distribution as a product suitable for curling.

In addition, the above artificial hair fiber may be a fiber having a monolayer structure. In this case, the inside of the fiber has less distortion resulting from layer formation, which improves qualities such as curl uniformity. In addition, as used herein, the fiber having a monolayer structure is not particularly limited unless the fiber has a circular borderline formed when the cross section of any one site of the fiber is observed with a scanning electron microscope. For example, the fiber is cut at 10 locations, and the cross-sections of the fiber are observed with a scanning electron microscope. At this occasion, if one of the cross sections does not form a circular borderline, the fiber is included in the above fiber having a monolayer structure. In addition, the above fiber having a monolayer structure can be produced by a typical process for producing an artificial hair fiber unless the fiber is subjected to melt-spinning to form two or more layers within the fiber in order to make the fiber have high performance during its production. For example, the fiber can be produced by a production method described below in Example 1. Of note is that examples of the above fiber having a monolayer structure include a fiber which is ejected from a nozzle during the melt-spinning step and then is coated with some thin film, which results in formation of a coating layer on the fiber surface. This is because, in general, the main structure of the fiber has been formed before ejection of the fiber through the nozzle at melt-spinning, and the following coating using the thin film hardly greatly reduces qualities of the fiber.

As stated herein, the KES method is an abbreviation of Kawabata Evaluation System and is one to measure the repulsive forces at various curvatures when a fiber structure is bent by using a KES flexural property-measuring machine (KES-FB2-SH, manufactured by KATO TECH CO., LTD.), as disclosed by Tokio Kawabata in the Journal of the Textile Machinery Society of Japan (Textile Engineering), vol. 26, No. 10, p. 721-728 (1973). And, in the measurement regarding this embodiment, an average value of repulsive forces of monofilament within a curvature range of from 0.5 to 1.5 is measured. By measuring the repulsive forces of monofilament, the rigidity of the fiber bundle is specified.

The flexural rigidity value by the KES method can be controlled, for example, by controlling the spinneret temperature of a nozzle at the time of melt-spinning. The flexural rigidity can be made low by lowering the spinneret temperature of the nozzle. By reducing the monofilament fineness of the fiber, the flexural rigidity can be made low. Further, in the case of using a fiber having a cross sectional shape with high bulkiness, the flexural rigidity becomes high, and in the case of a cross sectional shape with low bulkiness, the flexural rigidity becomes low. The sectional shape of the fiber with high bulkiness in the widthwise direction may, for example, be a Y-shape, an H-shape, a U-shape, a C-shape, or an X-shape. The sectional shape of the fiber with low bulkiness in the widthwise direction may, for example, be an elliptical shape, a circular shape, a cocoon shape, a 6-leaf flower shape, or an 8-leaf flower shape.

In order to match the fiber with the flexural rigidity described below, the sectional shape of an artificial hair fiber of this embodiment in the widthwise direction is preferably an elliptical shape, a circular shape, a glasses shape, a cocoon shape, a 6-leaf flower shape, or an 8-leaf flower shape.

Another embodiment of the present invention is an artificial hair fiber having a flexural rigidity of from 0.001 to 0.01 gf·cm², as measured by the KES method, and having a wave shape of the fiber within a range satisfying the following formulae:

0.2 mm≦R≦3 mm, 1 mm≦L≦15 mm,

(R: amplitude of a wave of the fiber in the widthwise direction, see FIG. 1), and (L: a cycle length of a wave of the fiber in the lengthwise direction, see FIG. 1).

The above artificial hair fiber is excellent in the hackling efficiency and the better weaving efficiency. In addition, the fiber is also excellent in the feel, and is thus preferable for a woven hair decoration. Examples of the woven hair decoration as used herein include a hair decoration which has been in a woven state at sales or distribution stage, or a hair decoration which is on sales or distribution as a product suitable for weaving. In addition, examples of the woven hair decoration include a braid, an extension hair, and the like.

The amplitude R is between 0.2 and 3 mm, and preferably between 0.3 and 2 mm. When the amplitude is moderately large, the effect of gear-crimping is properly obtained. In this case, tangles occur, to some extent, among fibers of a fiber bundle for artificial hair, and thus the artificial hair fibers do not readily slip on one another and the weaving efficiency thereof tends to be enhanced. In addition, when the amplitude R is moderately small, the wave shape of the artificial hair fiber is not likely to be rough, and the artificial hair fibers tend not to easily get caught during hackling.

The cycle length L is between 1 and 15 mm, and preferably between 2 and 10 mm. When the cycle length L is moderately large, the wave shape of the artificial hair fiber tends not to be rough, and thus the artificial hair fibers tends not to easily get caught during hackling. In contrast, when the cycle length L is moderately small, tangles occurs, to some extent, among the fibers of a fiber bundle for artificial hair, and thus the artificial hair fibers do not readily slip on one another and the weaving efficiency thereof tends to be enhanced.

When the wave shape of the artificial hair fiber meets a range of the above formulae, the cross-sectional shape of an artificial hair fiber of an embodiment is preferred to be a single or mixed shape selected from a circular shape, a cocoon shape, a Y-shape, an H-shape, and an X-shape. These shapes are suitable for maintaining a uniform crimping effect

As used herein, the artificial hair fiber has a fineness of monofilament of preferably between 20 and 100 decitex, and more preferably between 35 and 80 decitex. When the fineness of monofilament is moderately large, there is a tendency that the artificial hair fiber has a moderate hardness, the shape retention of the wave shape of the fiber is enhanced, and thus the qualities of the fiber is enhanced. In contrast, when the fineness of monofilament is moderately small, there is a tendency that the flexural rigidity does not become too large, and thus becomes moderate. Therefore, there is a tendency that the feel becomes soft and natural, and the weaving efficiency is improved.

As used herein, the artificial hair fiber is preferably an artificial hair fiber which is formed of at least one selected from the group consisting of a polyvinyl chloride resin, a polyester resin, and a polyamide resin.

When the wave shape of the artificial hair fiber meets a range of the above formulae, a synthetic resin which forms the artificial hair fiber can employ all the synthetic resins which allow for fiber formation, the resins including a vinyl chloride resin, a modacrylic resin, an acrylic resin, a polyethylene terephthalate resin, a polypropylene resin, a nylon resin, a polylactic acid resin, a polyvinyl alcohol resin, and the like. Among them, in view of the properties such as the strength, gloss, color hue, flame retardancy, touch, and thermal shrinkage property, preferred is a vinyl chloride resin, a mixed form of a vinyl chloride resin and a chlorinated vinyl chloride resin, or a modacrylic resin.

When a vinyl chloride resin is herein used as a synthetic resin which forms an artificial fair fiber, the vinyl chloride resin may be obtained by bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, or the like. However, it is preferred to use one produced by suspension polymerization, in consideration of, e.g., the initial coloration of the fibers. The vinyl chloride resin as used herein may be a homopolymer resin as a homopolymer of vinyl chloride or various types of copolymer resins. Examples of such a copolymer resin include a copolymer resin of vinyl chloride with a vinyl ester (e.g., a vinyl chloride/vinyl acetate copolymer resin, a vinyl chloride/vinyl propionate copolymer resin), a copolymer resin of vinyl chloride with an acrylate (e.g., a vinyl chloride/butyl acrylate copolymer resin, a vinyl chloride/2-ethylhexyl acrylate copolymer resin), a copolymer resin of vinyl chloride with an olefin (e.g., a vinyl chloride/ethylene copolymer resin, a vinyl chloride/propylene copolymer resin), and a vinyl chloride/acrylonitrile copolymer resin. It is particularly preferred to use, for example, a homopolymer resin as a homopolymer of vinyl chloride, a vinyl chloride/ethylene copolymer resin, or a vinyl chloride/vinyl acetate copolymer resin. In such a copolymer resin, the content of the comonomer may be determined depending upon the required quality such as molding processability and yarn properties. In addition, when the vinyl chloride resin is used for an artificial hair fiber, a larger content of the vinyl chloride resin can reduce the cost more. Accordingly, the content is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more, and still more preferably 95% by weight or more.

The viscosity-average polymerization degree of the vinyl chloride resin is preferably from 600 to 2500. When the polymerization degree is moderately large, there is a tendency that the melt viscosity does not decrease, and thus the resulting fiber is not susceptible to heat shrinkage. In addition, when the polymerization degree is moderately small, there is a tendency that the melt viscosity becomes low and thus the nozzle pressure becomes low. Thus, the production is likely to be carried out safely. Here, the viscosity-average polymerization degree is obtained by dissolving 200 mg of the resin in 50 ml of nitrobenzene and measuring the specific viscosity of this polymer solution in a 30° C. constant temperature tank by using an Ubbelohde viscometer, followed by calculation in accordance with JIS K6720-2.

A chlorinated vinyl chloride resin is preferably further incorporated into the vinyl chloride resin, whereby slippage of fibers of the fiber bundle for artificial hair from one another can be suppressed, and the weaving efficiency at the time of processing into a braid may be improved.

With respect to the formulation amount of the chlorinated vinyl chloride resin, the chlorinated vinyl chloride resin is preferably from 0.5 to 10 parts by mass per 100 parts by mass of the vinyl chloride resin, and more preferably from 1 to 5 parts by mass. A more formulation amount of the chlorinated vinyl chloride resin tends to suppress the slippage of fibers of the fiber bundle for artificial hair from one another. A less formulation amount causes less surface roughness of the artificial hair fiber and induces a soft feel. This is likely to reduce a risk of damaging hands at the time of weaving the fiber bundle for artificial hair, and thus the weaving efficiency can improve.

The viscosity-average polymerization degree of the chlorinated vinyl chloride resin is preferably from 450 to 800. An increased viscosity-average polymerization degree tends to cause the artificial hair fiber to be less susceptible to heat shrinkage. In addition, a decreased viscosity-average polymerization degree may decrease the melt viscosity so that the nozzle pressure becomes low. Thus, the production is likely to be carried out safely. Here, the viscosity-average polymerization degree is obtained by dissolving 200 mg of the resin in 50 ml of nitrobenzene and measuring the specific viscosity of this polymer solution in a 30° C. constant temperature tank by using an Ubbelohde viscometer, followed by calculation in accordance with JIS K6720-2.

When the vinyl chloride resin is used as a synthetic resin which forms an artificial hair fiber, a conventionally known additive is formulated into the vinyl chloride resin depending on the purpose. The additive may, for example, be a thermal stabilizer, a plasticizer, a lubricant, a compatibilizing agent, a processing aid, a reinforcing agent, an ultraviolet absorber, an antioxidant, an antistatic agent, a filler, a flame retardant, a pigment, an initial coloration-improving agent, an electrical conductivity-imparting agent, a surface treating agent, a photostabilizer, or a perfume.

When the polyester resin is used as a synthetic resin which forms an artificial hair fiber, examples of the polyester resin include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and the like.

When the polyamide resin is used as a synthetic resin which forms an artificial hair fiber, examples of the polyamide resin include nylon 6, nylon 66, nylon 11, nylon 12, nylon 6/10, nylon 6/12, and copolymers thereof. Preferred is nylon 6, nylon 66, or a copolymer of nylon 6 and nylon 66. In addition, when the polyamide resin is used as a primary synthetic resin which forms an artificial hair fiber, a more content of the polyamide resin can enhance a feel. Thus, the content is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more, and still more preferably 95% by weight or more.

When a bundle of artificial hair fibers according to this embodiment constitutes 90% or more of the total number among all the fibers, the fiber bundle for artificial hair is excellent in handling at the hand work and can be used for a braid and an extension hair etc.

Artificial hair fibers of this embodiment become a fiber bundle for artificial hair by bundling the fibers. The fibers may be used for a hair decoration such as wigs, hair pieces, braids, extension hairs, and doll hairs. A fiber bundle which has been subjected to crimping such as gear-crimping described below is preferable for, in particular, a braid or extension hair, etc., among fiber bundles for head decoration.

As used herein, a fiber bundle for artificial hair may be a bundle including one type of original yarn. Use of the one type of original yarn can achieve better processing efficiency and productivity.

With regard to an artificial hair fiber as used herein, types of a synthetic resin which serves as a raw material for the artificial hair fiber are not particularly limited, but the resin may have 10 types or less, preferably 7 types or less, more preferably 5 types or less, still more preferably 3 types or less, still more preferably 2 types or less, and still more preferably one type. When the number of the types of the raw material of the artificial hair fiber is small, the inside of the fiber has less distortion resulting from nonuniformity of the components, which improves qualities such as curl uniformity. In addition, the production step is more simplified, which leads to an effect of improving production efficiency as well.

Embodiment 2 Process for Producing an Artificial Hair Fiber by Using a Polyamide Resin as a Raw Material

Another embodiment of the present invention provides a process for producing an artificial hair fiber formed by using a polyamide resin as a raw material, the process comprising: a melt-spinning step of melt-spinning a polyamide resin at a spinneret temperature of 260 to 300° C.; and a stretching step of stretching melt-spun fibers under an atmosphere having a stretching temperature of 90 to 120° C. at a stretching ratio of 200 to 400%.

This production process can yield an artificial hair fiber having a flexural rigidity of from 0.001 to 0.01 g·cm² as measured by the KES method.

In addition, a process for producing an artificial hair fiber formed by using the above polyamide resin as a raw material may include a thermal relaxing step of subjecting the fibers stretched at the above stretching step to thermal relaxing treatment under an atmosphere of air at a temperature of 140 to 240° C. until the entire length of the fibers becomes 60 to 100% of the length before the treatment. In this case, the resulting artificial hair fiber can decrease the thermal shrinkage rate even more.

When the temperature under an atmosphere of air during the thermal relaxing step is Moderately high, the effect of decreasing the thermal shrinkage rate is not reduced, there is a tendency that the yarn is difficult to be slacked off, and thus the production is easy. In addition, when the temperature is not too high, the fibers can be more resistant against shrinkage stress, and there is a tendency that the yarn is not cut or the color of the yarn does not change during the production. Because of this, in a process for producing an artificial hair fiber formed by using the above polyamide resin as a raw material, the temperature is preferably between 140 and 240° C. This thermal relaxing step enables the entire length of the fibers to become 60 to 100% of the length after the stretching step.

Embodiment 3 Process for Producing an Artificial Hair Fiber by Using a Vinyl Chloride Resin as a Raw Material

Another embodiment of the present invention provides a process for producing an artificial hair fiber formed by using a vinyl chloride resin as a raw material, the process comprising:

-   -   a mixing step of mixing a vinyl chloride resin and an additive;     -   a melt-spinning step of melt-spinning a composition containing         the mixed vinyl chloride resin at a spinneret temperature of 160         to 190° C.;     -   a stretching step of stretching melt-spun fibers under an         atmosphere at a stretching temperature of 90 to 120° C., at a         stretching ratio of 200 to 400%; and     -   a thermal relaxing step of subjecting the stretched fibers to         thermal relaxing treatment under an atmosphere of air at a         temperature of 110 to 140° C. until the entire length of the         fibers becomes 60 to 95% of the length before the treatment.

This production process can yield an artificial hair fiber having a flexural rigidity of from 0.001 to 0.01 gf·cm² as measured by the KES method.

Another embodiment of the present invention provides a process for producing an artificial hair fiber formed by using a vinyl chloride resin as a raw material, the process comprising:

-   -   a mixing step of mixing a vinyl chloride resin and an additive;     -   a melt-spinning step of melt-spinning a composition containing         the mixed vinyl chloride resin at a spinneret temperature of 160         to 190° C.;     -   a stretching step of stretching melt-spun fibers under an         atmosphere at a stretching temperature of 90 to 120° C., at a         stretching ratio of 200 to 400%;     -   a thermal relaxing step of the stretched fibers to thermal         relaxing treatment under an atmosphere of air at a temperature         of 110 to 140° C. until the entire length of the fibers becomes         60 to 95% of the length before the treatment; and     -   a crimping step of crimping the fibers after the thermal         relaxing treatment step.

This production process includes subjecting the fibers following the above thermal relaxing treatment step to appropriate crimping, and thus can readily produce an artificial hair fiber having a wave shape of the fiber within a range satisfying the following formulae:

02 mm≦R≦3 mm, 1 mm≦L≦15 mm,

-   -   (R: amplitude of a wave of the fiber in the widthwise direction,         see FIG. 1), and     -   (L: a cycle length of a wave of the fiber in the lengthwise         direction, see FIG. 1).

For the melt-spinning step, a single screw extruder, a counter-rotating twin screw extruder, or a conical twin screw extruder, etc., can be used. Specifically, a pellet compound, etc., containing a resin composition is subjected to melt-spinning by using these extruders at a spinneret temperature of 160 to 190° C., and more preferably from 165 to 185° C. Here, when the spinneret temperature is moderately high, the obtained fibers are provided with moderate flexural rigidity having moderate hardness. In contrast, when the spinneret temperature is moderately low, the obtained fibers are provided with moderate flexural rigidity having natural flexibility.

In terms of the extruder used for the melt-spinning step, it is better to use a single screw extruder having a bore diameter of from 35 to 85 mm or a conical extruder having a bore diameter of from 35 to 50 mm. A small bore diameter reduces an extrusion amount. Such small bore diameter is preferable because the nozzle pressure becomes low and the flow-out speed of non-stretched yarn becomes slow, which is likely to make winding easy.

In a manner similar to the preceding embodiments, an artificial hair fiber of this embodiment has a fineness of monofilament of preferably between 20 and 100 decitex, and more preferably between 35 and 80 decitex. In order to achieve this fineness of monofilament, it is preferable that fibers immediately after the melt-spinning step (non-stretched fibers) have a fineness of 300 decitex or less. When the fineness of the non-stretched fibers is low, the stretching ratio may be low so as to obtain an artificial hair fiber having a fine fineness. This is because gloss does not readily occur on the artificial hair fiber following the stretching treatment, so that it tends to become easy to maintain the level of a medium gloss to 70% gloss state.

The cross sectional area of a nozzle used for melt-spinning may be, but is not particularly limited to, between 0.1 and 2 mm. In addition, quality aspects of artificial hair such as a curling property are taken into account, it is preferable to make the fibers melt and eject from a nozzle having nozzle holes each having a cross sectional area of 0.5 mm² or less. This is because when one nozzle hole has a cross sectional area of less than 0.5 mm², the tension to produce a non-stretched yarn having a fine fineness or a hot-spun yarn can be suppressed to a low level, which results in reduced residual distortion. Besides, the qualities such as curl retention does not readily decrease.

At the time of melt-spinning, the nozzle pressure is preferably 50 MPa or less. When the nozzle pressure is moderately low, there is a tendency that a load applied to the thrust portion of an extruder decreases and thus the extruder is less likely to be damaged. Besides, there is also a tendency that a resin leakage from a turn head or die, etc., is less likely to occur.

The spinneret used for melt-spinning may employ a spinning spinneret whose nozzle has one or more shapes selected from the group consisting of a circular shape, a cocoon shape, a Y-shape, an H-shape, and an X-shape. Since these spinnerets fail to have a complicated shape, fibers corresponding to the spinneret can be easily produced. Additionally, fibers as prepared using these spinnerets are easy to maintain their shape, and their processing is relatively easy as well.

During the stretching step of stretching the melt-spun fibers under an atmosphere at a stretching temperature of 90 to 120° C. at a stretching ratio of 200 to 400%, fibers having a fine fineness of 100 decitex or less can be obtained from the melt-spun fibers.

When the stretching temperature is too low, the strength of the fibers becomes low. Also, there is a tendency that yarn breakage easily occurs. When the temperature is too high, the feel of the resulting fibers tends to become a smooth feel like a plastic. Accordingly, the temperature is required to be between 90 and 120° C. When the stretching ratio is moderately large, there is a tendency that the fibers are moderately strengthened. When the stretching ratio is moderately small, there is a tendency that yarn breakage is difficult to occur during the stretching treatment. Thus, the ratio is required to be between 200 and 400%.

In this embodiment, the thermal relaxing step is adopted. This is because the thermal shrinkage rate of the resulting artificial hair fiber is made lower. The thermal relaxing treatment can be carried out consecutively after the stretching treatment or carried out with an interval after the fibers are once wound up.

When the temperature under an atmosphere of air during the thermal relaxing step is moderate, the effect of decreasing the thermal shrinkage rate is not reduced, there is a tendency that the yarn is difficult to be slacked off, and thus the production is easy. In addition, when the temperature is not too high, the fibers can be more resistant against shrinkage stress, and there is a tendency that the yarn is not cut or the color of the yarn does not change during the production. Accordingly, in a process for producing an artificial hair fiber formed by using a vinyl chloride resin as a raw material, the temperature is preferably between 110 and 140° C. This thermal relaxing step enables the entire length of the fibers to become 60 to 95% of the length following the stretching step.

The above crimping step is a step to give an artificial hair fiber the amplitude (wave shape).

Strong crimping causes the weaving efficiency to become better, but tends to exacerbate a catch during hackling. In contrast, weak crimping causes the catch to improve during the hackling. However, the weaving efficiency tends to be deteriorated. This balance should be kept.

Examples of this crimping step include gear-crimping and a woolly processing method, and the step preferably use the gear-crimping.

This gear-crimping is a process including carrying out crimping by making a fiber bundle pass through between two engaging gears at a high, temperature.

The gear-crimping can control the wave shape of an artificial hair fiber by regulating the depth of gear waves, the gear surface temperature, and the processing rate. When the depth of gear waves is moderately large, there is a tendency that crimps are moderately strong and thus moderate amplitude is provided to the artificial hair fiber. In addition, when the depth of gear waves is moderately small, there is a tendency that the crimps is not too strong and thus the amplitude of the artificial hair fiber is reduced. Therefore, the depth is preferably between 0.2 mm and 6 mm, and more preferably between 0.5 mm and 5 mm.

When the gear surface temperature is moderately high, there is a tendency that the crimps are moderately strong and amplitude is provided to the artificial hair fiber. When the gear surface temperature is moderately high, there is a tendency that the crimps are not too strong and thus the amplitude of the artificial hair fiber is reduced. Therefore, the temperature is preferably between 30 and 100° C., and more preferably between 40 and 80° C.

When the gear processing rate is moderately high, there is a tendency that the amplitude of the artificial hair fiber is reduced. In addition, when the gear processing rate is moderately low, there is a tendency that the crimps are moderately strong and amplitude is provided to the artificial hair fiber. Therefore, the rate is preferably from 0.5 to 10 m/min, and more preferably from 1.0 to 8.0 m/min.

Preheating of the artificial hair fibers before they pass through gears can yield more stable productivity and a uniform wave shape by avoiding rapid heating.

When the total fineness of a fiber bundle at the time of gear-crimping is moderately large, there is a tendency that yarn breakage is difficult to occur during the crimping, and the productivity is enhanced. In addition, when the total fineness of a fiber bundle at the time of gear-crimping is moderately low, there is a tendency that a uniform wave shape can be easily obtained. Accordingly, the fineness is preferably between 100 thousand and 2 million decitex, and more preferably between 500 thousand and 1.5 million decitex.

In addition, the gear-crimping requires a relatively short period of heating the fibers. So, there is a little evaporation of the water content from the inside of the fibers during the crimping, and there is less yarn breakage or damage as well. For the artificial hair fibers, the water content is a key element to make the fibers have a moist feeling which approaches that of natural hair. Therefore, the artificial hair fibers as prepared using the gear-crimping can be said to have increased qualities and productivity. Also, the gear-crimping does not require prolonged work, and also does not need a complicated apparatus or complicated steps. Accordingly, it is a processing procedure excellent in performance, productivity, or precision. Furthermore, its high controllability makes this processing procedure suitable for adding a desired wave shape to the fibers.

EXAMPLES

Hereinafter, by referring to Examples and Comparative Examples while Table 1, Table 2, and FIG. 1 are taken into consideration, the present invention is described in detail.

TABLE 1 Example Comparative Example 1 2 3 4 1 2 3 Flexural 0.0035 0.0032 0.0046 0.0065 0.0005 0.0120 0.0115 rigidity (gf/cm²) Resin Polyamide- Vinyl Polyamide- Vinyl Polyamide- Polyamide- Vinyl based Chloride- based Chloride- based based Chloride- based based based Nozzle Round Round Cocoon H-Shape Cocoon H-Shape Round Shape Fineness of 58 62 74 68 31 94 110 Monofilament (decitex) Curl Excellent Excellent Excellent Excellent Poor Excellent Excellent Uniformity 0.83 0.86 0.80 0.89 0.62 0.93 0.92 Feel Excellent Excellent Excellent Excellent Excellent Poor Poor

In Table 1 and Table 2, the “flexural rigidity” was determined using KES-FB2-SH manufactured by KATO TECH CO., LTD. The sample was one fiber having a length of 9 cm, and it was passed through a jig having a diameter of 0.2 mm, whereupon a pure bending test was carried out at a deformation speed of 0.2 (cm⁻¹) within a curvature range of −2.5 to +2.5 (cm⁻¹) while the “SENS setting” of a software was set to 2×5 and the “SENS setting” of the instrument was set to 0.08. An average value of repulsion forces with a monofilament within a curvature range of from 0.5 to 1.5 was measured, and a numerical value was estimated by the indicated value divided by 50.

In Table 1, the “curl uniformity” was measured as follows. First, a fiber (hot-spun yarn) bundle including 120 monofilaments was cut at a certain constant length. The bundle was made to be wound around an aluminum cylinder having a 20 mm φ, immobilized at both ends, thrown into an air-circulating oven at 100° C., and heated for 30 minutes. Next, the aluminum cylinder (with the fibers wound) was left at a temperature of 23° C. in an incubator having a relative humidity of 50% for 24 hours. After that, the fiber bundle was removed from a stainless cylinder, and was suspended by fixing one end of the bundle. At that time, an angle of a root curled shape at a top (bottom) portion and an angle of a tip curled shape at a top (bottom) portion were determined. The curl uniformity was estimated by dividing the angle of a tip curled shape by the angle of a root curled shape in accordance with the following criterion. The more closely the angle ratio approaches 1, the less the difference between the angles. This means that the curling prevails uniformly.

In Table 1 and Table 2, the term “feel” refers to an index representing a feel of a product The feel was evaluated under the following evaluation standards based on judgment by 10 technicians (with practical experience of at least 5 years) for treatment of artificial hair fibers.

Excellent: One evaluated by all the technicians to have a good feel;

Good: One evaluated by 80% or more of the technicians to have a good feel; and

Poor: One evaluated by 30% or more of the technicians to have a poor feel.

Example 1

First, 100 parts by mass of a nylon 6 resin (1013B, manufactured by UBE INDUSTRIES, LTD.) and 5 parts by mass of crosslinked acryl particles (MXB-2B, manufactured by SEKISUI CHEMICAL CO. LTD.) were blended with a hand. Then, the mixture was subjected to melt-spinning by using a spinning spinneret having a round nozzle shape, a nozzle cross sectional area of 0.2 mm², and a hole number of 20, at a cylinder temperature of 280° C. and at an extrusion amount of 1.0 kg/hour. After that, the fibers were stretched to 300% under an atmosphere of air at 100° C., and were subjected to thermal relaxing treatment under an atmosphere of air at 150° C. to yield polyamide fibers having a fineness of monofilament and a flexural rigidity value as shown in Table 1.

Example 2

First, 100 parts by mass of a vinyl chloride resin (TH-1000, manufactured by TAIYO VINYL CORP.), 3 parts by mass of a hydrotalcite type composite stabilizer (CP-410A, manufactured by Nissan Chemical Industries, Ltd.) (the thermal stabilizer component had 1.5 parts by mass), 0.5 parts by mass of an epoxidized soybean oil (O-130P, manufactured by Asahi Denka Kogyo K. K.), and 0.8 parts by mass of an ester lubricant (EW-100, manufactured by Riken Vitamin Co., Ltd.) were formulated into a vinyl chloride resin composition. Then, the composition was subjected to melt-spinning by using a spinning spinneret having a round nozzle shape, a nozzle cross sectional area of 0.06 mm², and a hole number of 120, at a cylinder temperature of 180° C. and at an extrusion amount of 10 kg/hour. After that, the fibers were stretched to 300% under an atmosphere of air at 100° C., and were subjected to thermal relaxing treatment under an atmosphere of air at 120° C. until the entire length of the fibers was shrunk to 75% of the length before the treatment. Finally, polyvinyl chloride fibers were yielded which have a fineness of monofilament and a flexural rigidity value as shown in Table 1.

Comparative Example 1, Comparative Example 2

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that the flexural rigidity and the fineness of monofilament as shown in Table 1 were achieved using melt-spinning by changing the nozzle shape to an elliptical shape in Comparative Example 1 and by changing the nozzle shape to an H-shape in Comparative Example 2.

TABLE 2 Example 1 2 3 4 5 6 7 8 9 R (mm) 0.7 0.2 2.5 0.7 0.7 0.7 0.7 0.7 0.7 L (mm) 5 5 5 1.5 12 5 5 5 5 Flexural 0.004 0.004 0.004 0.004 0.004 0.001 0.009 0.004 0.004 rigidity (gf/cm²) Nozzle Shape H H H H H Cocoon X H H Fineness of 67 67 67 67 67 67 67 67 67 Monofilament (decitex) Resin Vinyl 100 100 100 100 100 100 100 100 100 Chloride Resin Chlorinated 0 0 0 0 0 0 0 3 15 Vinyl Chloride Resin Hackling Exc. Exc. Good Good Exc. Exc. Exc. Exc. Exc. Loss (%) 0.3 0.1 0.8 0.7 0.1 0.3 0.4 0.3 0.4 Weaving Exc. Good Exc. Exc. Good Exc. Good Exc. Good Efficiency Proportion Exc. Exc. Exc. Exc. Exc. Good Exc. Exc. Exc. of Crimped 98 97 97 98 96 91 97 97 98 Fibers (%) Feel Exc. Exc. Exc. Exc. Exc. Exc. Good Exc. Good Comparative Example 1 2 3 4 5 6 R (mm) 0.1 4 0.7 0.7 0.7 0.7 L (mm) 5 5 0.5 20 5 5 Flexural 0.004 0.004 0.004 0.004 0.0005 0.012 rigidity (gf/cm²) Nozzle Shape H H H H Cocoon X Fineness of 67 67 67 67 31 89 Monofilament (decitex) Resin Vinyl 100 100 100 100 100 100 Chloride Resin Chlorinated 0 0 0 0 0 0 Vinyl Chloride Resin Hackling Exc. Poor Poor Exc. Exc. Exc. Loss (%) 0.2 1.3 1.3 0.3 0.3 0.4 Weaving Poor Exc. Exc. Poor Good Good Efficiency Proportion Exc. Exc. Exc. Exc. Poor Exc. of Crimped 98 96 97 97 86 99 Fibers (%) Feel Exc. Exc. Exc. Exc. Exc. Poor Exc. = Excellent

In Table 2, the term “hackling loss” refers to an index of catch during hackling. A fiber bundle which has been subjected to gear-crimping is cut at a length of 1 m. Then, 100 g of the bundle is weighed. Fibers which get caught with a metal brush and are cleaved during 10 times of hackling are expressed as percent by weight. The lower the percent by weight of the cleaved fibers, the less the fibers get caught, which indicates a better hackling efficiency. This was evaluated based on the following evaluation standards.

Excellent: The percent by weight is less than 0.5%.

Good: The percent by weight is between 0.5% and less than 1.0%.

Poor: The percent by weight is 1.0% or more.

In Table 2, the term “weaving efficiency” refers to an index indicating an easy-to-weave characteristic. The weaving efficiency was evaluated from the intensity of crimping under the following evaluation standards based on judgment by 10 technicians (with practical experience of at least 5 years) for treatment of artificial hair fibers.

Excellent: One evaluated by all the technicians to be easy to weave and thus being excellent in weaving efficiency.

Good: One evaluated by 80% or more of the technicians to be easy to weave and thus being good in weaving efficiency.

Poor: One evaluated by 30% or more of the technicians to be difficult to weave and thus being poor in weaving efficiency.

In Table 2, the term “proportion of crimped fibers” refers to an index indicating a quality of the product. After the gear-crimped fiber bundle was hackled, 100 fibers were selected at random. A proportion of the post-crimping fibers satisfying the following formulae was determined by counting the number.

0.2 mm≦R≦3 mm, 1 mm≦L≦15 mm:

(R: amplitude of a wave of the fiber in the widthwise direction), and

(L: a cycle length of a wave of the fiber in the lengthwise direction).

As the proportion of the crimped fibers satisfying the above formulae becomes higher, it represents that the product has a more excellent quality. This was evaluated by the following evaluation standards.

Excellent: The proportion of the crimped fibers is 95% or more.

Good: The proportion of the crimped fibers is between 90% and less than 95%.

Poor: The proportion of the crimped fibers is less than 90%.

Example 1

Polyvinyl chloride fibers (A) having a fineness of monofilament and a flexural rigidity value as shown in Table 2 were obtained by the successive steps comprising:

(a) mixing with a Henschel mixer a vinyl chloride resin composition comprising 100 parts by mass of a vinyl chloride resin (TH-1000, manufactured by TAIYO VINYL CORP.), 3 parts by mass of a hydrotalcite type composite stabilizer (CP-410A, manufactured by Nissan Chemical Industries, Ltd.)(the thermal stabilizer component had 1.5 parts by mass), 0.5 parts by mass of an epoxidized soybean oil (O-130P, manufactured by Asahi Denka Kogyo K. K.), and 0.8 parts by mass of an ester lubricant (EW-100, manufactured by Riken Vitamin Co., Ltd.);

(b) melt-spinning the mixed resin composition by using a spinning spinneret having an H-shape nozzle, a nozzle cross sectional area of 0.06 mm², and a hole number of 120, at a spinneret temperature of 170° C. and at an extrusion amount of 10 kg/hour, and then yielding fibers having 150 decitex;

(c) stretching the melt-spun fibers to 300% under an atmosphere of air at 100° C.; and

(d) subjecting the stretched fibers to thermal relaxing treatment under an atmosphere of air at 120° C. until the entire length of the fibers is shrunk to 75%.

(e) A fiber bundle for artificial hair satisfying R value (the length from the top to the bottom of a crimp wave shape) as shown in Table 2 was obtained by making fibers (A) bundle into a fiber bundle having a total fineness of one million, and by gear-crimping the bundle by using brass gears (diameter 13 cm, distance between gear waves: 2.5 mm, depth of gear waves: 2.5 mm) at a gear surface temperature of 50° C. and at a processing rate of 2.5 m/min.

Example 2, Example 3

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that the processing condition for the gear-crimping in Example 1 was changed to the R value shown in Table 2.

Example 4, Example 5

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that the processing condition for the gear-crimping in Example 1 was changed to the L value shown in Table 2.

Example 6, Example 7

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that the nozzle shape of step (B) in Example 1 was changed to a cocoon shape in Example 6 and changed to an X shape in Example 7 to achieve the flexural rigidity as shown in Table 2.

Example 8, Example 9

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that in step (a) of Example 1, a chlorinated vinyl chloride resin (HA-15E, manufactured by TAIYO VINYL CORP.) was formulated in an amount as shown in Table 2.

Comparative Example 1, Comparative Example 2

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that the processing condition for the gear-crimping in Example 1 was changed to the R value shown in Table 2.

Comparative Example 3, Comparative Example 4

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that the processing condition for the gear-crimping in Example 1 was changed to the L value shown in Table 2.

Comparative Example 5, Comparative Example 6

A fiber bundle for artificial hair was obtained in the same manner as in Example 1 except that the flexural rigidity and the fineness of monofilament as shown in Table 2 were achieved using melt-spinning in step (b) of Example 1 by changing the nozzle shape to an elliptical shape to produce 70-decitex fibers in Comparative Example 5 and by changing the nozzle shape to an X-shape to produce 250-decitex fibers in Comparative Example 6.

<Discussion of Results>

As described in Table 1, fibers having a rigidity with a range from 0.001 to 0.01 gf/cm² resulted in both excellent curl uniformity and feel. Specifically, the present invention was able to produce artificial hair fibers or a fiber bundle for artificial hair having a good balance between a single (i.e., even one type) feel and a curly characteristic. It is notable that a key factor which makes the curl uniformity of fibers and their feel excellent remains unclear. It seems that a nozzle shape or a type of resin may largely affect them. Here, Examples of the present application demonstrated that they largely depend on the rigidity of fibers having a range between 0.001 and 0.01 gf/cm². This was a remarkable finding.

As shown in Table 2, all of the hackling efficiency, weaving efficiency, and feel were excellent when the fibers had a rigidity with a range from 0.001 to 0.01 gf/cm², and the fibers had a wave shape with a range satisfying the following formulae: [0.2 mm≦R≦3 mm, 1 mm≦L≦15 mm, (R: amplitude of a wave of the fiber in the widthwise direction), and (L: a cycle length of a wave of the fiber in the lengthwise direction)]. That is, the present invention enabled a fiber bundle for artificial hair having an excellent weaving efficiency and feel to be produced almost without getting caught during hackling when the fibers had a specific wave shape.

Here, in Examples 1 to 5, 8, and 9, the nozzle shape of the spinning spinneret was an H-shape. This was totally unexpected from the results disclosed in WO2008/035712. This WO2008/035712 describes that when the spinneret having a double-cross shape or triple-cross shape was used, the hackling efficiency, easy-to-weave characteristic, and feel improved, but when the spinneret having an H-shape or Y-shape was used, they failed to improve. Accordingly, it was remarkable results that in Examples 1 to 5, 8, and 9, in spite of using the spinneret having an H-shape, all of the hackling efficiency, weaving efficiency, and feel exhibited excellent outcomes.

Excellent outcomes were yielded not only for an H-shape in Table 2 of the present application, but also for a cocoon shape (Example 6) and an X-shape (Example 7). From the above results, it seems that fibers in which all of the hackling efficiency, weaving efficiency, and feel as obtained in the present invention are excellent correspond to a broad range of their cross-sectional shape.

DESCRIPTION OF SYMBOLS

-   -   R: Length from the top to the bottom of a crimp wave shape.     -   L: Length between the tops (or between the bottoms) of a crimp         wave shape. 

1. An artificial hair fiber, which is a fiber having a flexural rigidity of from 0.001 to 0.01 gf·cm² as measured by the KES method, wherein the fiber is formed of a synthetic resin.
 2. The artificial hair fiber according to claim 1, wherein a sectional shape of the fiber in the widthwise direction is an elliptical shape, a circular shape, a glasses shape, a cocoon shape, a 6-leaf flower shape, or a 8-leaf flower shape; or the mixed shape thereof.
 3. The artificial hair fiber according to claim 1, wherein the synthetic resin is a polyvinyl chloride resin.
 4. The artificial hair fiber according to claim 3, wherein the fiber is a polyvinyl chloride fiber produced by melt-spinning the polyvinyl chloride resin.
 5. The artificial hair fiber according to claim 3, wherein the polyvinyl chloride resin comprises 100 parts by mass of a vinyl chloride resin and 0.5 to 10 parts by mass of a chlorinated vinyl chloride resin.
 6. The artificial hair fiber according to claim 1, wherein the synthetic resin is at least one synthetic resin selected from the group consisting of nylon 6, nylon 6/6, nylon 4/6, nylon 1/2, nylon 6/10, and nylon 6/12.
 7. The artificial hair fiber according to claim 1, wherein the synthetic resin is a modacrylic resin.
 8. The artificial hair fiber, wherein the artificial hair fibers according to claim 3 are blended.
 9. The artificial hair fiber according to claim 1, wherein a wave shape of the artificial hair fiber is within a range satisfying the following formulae: 0.2 mm≦R≦3 mm, 1 mm≦L≦15 mm, (R: amplitude of a wave of the fiber in the widthwise direction), and (L: a cycle length of a wave of the fiber in the lengthwise direction).
 10. The artificial hair fiber according to claim 9, wherein the wave shape of the artificial hair fiber is formed by gear-crimping.
 11. A fiber bundle for artificial hair, wherein obtained by bundling the artificial hair fibers according to claim
 1. 12. A curly hair decoration using the artificial hair fiber according to claim
 1. 13. A woven hair decoration using the artificial hair fiber according to claim
 1. 14. A braid using the artificial hair fiber according to claim
 1. 15. An extension hair using the artificial hair fiber according to claim
 1. 16. A process for producing an artificial hair fiber, the process comprising: a mixing step of mixing a vinyl chloride resin and an additive; a melt-spinning step of melt-spinning a composition containing the mixed vinyl chloride resin at a spinneret temperature of 160 to 190° C.; a stretching step of stretching melt-spun fibers under an atmosphere at a stretching temperature of 90 to 120° C., at a stretching ratio of 200 to 400%; a thermal relaxing step of subjecting the stretched fibers to thermal relaxing treatment under an atmosphere of air at a temperature of 110 to 140° C. until the entire length of the fibers becomes 60 to 95% of the length following the stretching step; and a crimping step of crimping the fibers after the thermal relaxing treatment step.
 17. The process for producing an artificial hair fiber according to claim 16, wherein the crimping is gear-crimping carried out at a depth of gear waves of 0.2 mm to 6 mm, a gear surface temperature of 30 to 100° C., and a processing rate of 0.5 to 10 m/min.
 18. The process for producing an artificial hair fiber according to claim 16, wherein an orifice shape of a spinneret as used in the melt-spinning step include a circular shape, a cocoon shape, a Y-shape, an H-shape, or an X-shape; and the spinneret has a single or mixed shape thereof. 